A 50 year old man, dangerously obese, goes to the hospital for experimental brain surgery to suppress his appetite. A small piece of his skull is removed, and an electrical probe inserted deep into his brain tissue. It reaches his hypothalamus and current is switched on. Suddenly the patient -- awake through the procedure -- begins to speak uncontrollably about events in his past, events he had long forgotten. He remembers a day's walk in the park 30 years ago, complete with what people were wearing, all in vivid color. He sees them speaking to him, every motion they made. The intensity and level of detail of the memories is frightening.

The scene may read like the script of a bad science fiction flick but it comes from an unidentified patient at Ontario's Toronto Western Hospital. No one was more astonished than the man's doctors, who began to experiment further on him. Over the next few weeks, they continued testing. His ability to both learn and remember was substantially increased when the electrodes were turned on. Continuous stimulation also had a residual effect -- after the electrodes were off, there was still a slight benefit.

Professor Andreas Lozano, of the Neurosurgery Department of Toronto Western, led the research. He says the electrodes function like "turning up the volume" on the brain's memory circuits. "As we turned the current up, we first drove his memory circuits and improved his learning. As we increased the intensity, we got spontaneous memories of discrete events. At a certain intensity, he would slash to the [park scene]. When the intensity was increased further, he got more detail but, when the current was turned off, it rapidly decayed."

Lozano's previous research included stimulating certain portions of the brain to curb appetite. His research in that field earned him more than a few headlines in 2006.

The results were so successful the same technique is now being trialed on six Alzheimer's patients. Functioning like a "pacemaker for the brain," the treatment offers hope for the millions worldwide who suffer from the debilitating memory and cognitive losses caused by Alzheimer's.

The electrodes are connected by a cable that runs under the patient's skin, down the back of the neck to a battery pack implanted in the patient's chest. A constant low-level current stimulates the brain tissue, but is otherwise imperceptible to the patient.

The devices are the same as those already being used successfully as a treatment for Parkinson's disease, severe depression, and even chronic pain; all that varies is the exact segment of the brain where implantation occurs. In Parkinson's, for instance, the subthalamic nucleus is stimulated. Depression targets a small area of the cingulate cortex.

"This gives us new insight into which brain structures are involved in memory", says Professor Lozano.

More news of Lozano's research is expected to be announced later today to Canadian media.